How to get cydia on ipod touch?

Can somebody please tell me exactly what do do on how to get Cydia for the ipod touch step by step. And another question, does Cydia break your ipod or jailbreaking it at all break it??? I've looked on yotube and everywhere on the internet so tell me how YOU did it if you have. When I try to do to jailbreakme.com it either goes to a screen full of letters or a picture of a guy snowboarding